Conversations with Nick Keiser: Social interactions and the spread of disease

Nick Keiser is a researcher at the University of Florida. He studies the behavioral mechanisms of infectious diseases. The main focus of lab centers on social animals and how their group behavior affects the transmission of infectious microbes. Keiser recently completed a study using fruit flies to investigate how social context influences the spread of disease. He discussed his findings with SCINQ.

SCINQ: What prompted you to investigate the ways social context may influence the transmission of disease?

NICK KEISER: The interaction between our own behavioral tendencies and the social environments that we experience is a huge determinant of life outcomes. In the infectious disease literature, there has been quite a bit of research trying to understand how these two factors can influence infection risk, but most of these studies are observational, correlative, or were being pursued in non-tractable study systems. I come from an animal behavior background and have recently started studying infectious disease ecology, so this seemed like a problem we could try to address in the lab.

SCINQ: Can you discuss how the experiment was designed?

We needed a test system where we could reliably acquire individual animals that behave in a certain way, and differ consistently from other individuals, and then manipulate the social environment around them. Fruit flies are a perfect system for that because we can use laboratory-maintained lineages of flies that originated from the wild and we know that they differ in their behavioral tendencies. Since our pathogen of interest, an entomopathogenic fungus, had previously been shown to be transmitted between sexual partners during copulation, we thought group sex ratio would be an important factor of the social’;. environment that could influence individuals’ social behaviors, mating dynamics, and infection risk.

SCINQ: Why did you choose fruit flies? How did you manipulate different social contexts?

NK: We have genetic lineages of fruit flies in the lab that we know vary from one another in their behavioral tendencies, like their social preferences, and I had the entomopathogenic fungus in the lab already from another study, so we were pretty well-suited to address the research questions using this system. To manipulate different social contexts, we simply varied the sex ratio (the relative proportion of
males and females) in the social groups from all males to all females, and three intermediate sex ratios. Then, to each group, we added a single male or female fly that had been exposed to infectious fungal conidiospores and let them all interact naturally.

SCINQ: What did you discover about the links between social context and transmission?

NK: We found that fly genotype and group sex ratio influenced flies’ aggregation behavior and mating dynamics. However, only group sex ratio influenced the prevalence of infection we observed in the social groups. On an individual level, we found that males were more likely to become infected when the first infected individual was female. Even more strikingly, we found that when the first infected individual was a male, flies that mated more often were more likely to become infected. But this trend totally disappeared in cases where the first infected fly was female. So disease dynamics were influenced by individual-level and group-level factors

SCINQ: Transmission in this experiment seems to be closely tied to mating behavior, but there were also instances of transmission from food patches or inadvertent contact with other infected fruit flies (presumable males). How were you able to differentiate between the different types of contact?

NK: Great question! The short answer is that we couldn’t, unfortunately. Since we observed every mating event that occurred, we know that virgins who became infected must have picked up the pathogen from another source, but we had no way of differentiating those sources after the experiment. It could have been from aggressive interactions, or from the shared food patch, or maybe just from courting an infected individual. We’re working on developing methods to identify different modes of transmission experimentally with the same pathogen – hopefully more to come from that in the future.

SCINQ: Can your findings be applied to animals with more complex social interactions?

NK: Although I am always wary of direct applications across biological systems, I think the idea that the social environment can change disease dynamics is undoubtedly widespread. Regardless of the complexity of social interactions in any given animal society, an individuals’ behaviors are intimately linked to the number and types of individuals with whom it interacts. Given that the first defense against many infectious diseases is behavioral (avoiding spoiled foods, assessing the infection status of social partners, etc.), these behaviors may also change across social contexts.

SCINQ: On a more personal note, how did you come to a life in science? Did you always want to be a scientist?

NK: I grew up in a Navy family, so we moved across the country many times when I was very young. This exposed me to so many great environments, but the ocean always fascinated me. So, like many biologists, I wanted to be a marine biologist as early as kindergarten. Then, there was also a brief affair with paleontology, but overall I’ve only ever wanted to be a biologist. I always found animal behavior fascinating, and spiders and insects are such great, tractable study systems for animal behavior. I still can’t believe I get to do this as a career, and I’m very fortunate that I get to help others pursue the same dream that I had.

SCINQ: What advice would you give to someone about to embark on doctoral work?

NK: Pursue a topic that you love, something that you’ll be excited to learn about every single day. But, don’t get married to any single idea. Research directions can change rapidly (sometimes even in the middle of experiments) and that’s not a bad thing! Don’t be afraid to chase new questions, side projects, and collaborations, even if
they’re very different from the ones you proposed in your dissertation proposal.

SCINQ: Who are your biggest professional influences?

NK: Functionally, a scientist’s biggest influences are often the advisors, mentors, and collaborators they acquire throughout their career. That’s why it is very important to surround yourself with people you enjoy working with, and with whom you want to establish long-term professional relationships.

SCINQ: Finally, where do you see yourself in ten years?

NK: I just started a new lab in the Department of Biology at the University of Florida focusing on the behavioral mechanisms of infectious disease ecology. So, in ten years I’d like to be leading a productive, diverse group of scientists in addressing their own research questions in my lab. I’m also an aspiring juggler, so there’s always the option of joining a circus.

For more information about Nick Keiser and his research, visit his lab page or follow him on Twitter @hidrnic.

IMAGE SOURCE: Jeff Fitlow; Creative Commons

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